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STABLE

Stabilization Table for Accurately Balancing a Loose Element. STABLE. Critical Design Review December 13th, 2012. William Brown Phillip Chen Eric Huckenpahler Laura Hughes Brian Ibeling Chris Johnson. Project Overview.

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STABLE

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  1. Stabilization Table for Accurately Balancing a Loose Element STABLE Critical Design Review December 13th, 2012 William Brown Phillip Chen Eric Huckenpahler Laura Hughes Brian Ibeling Chris Johnson

  2. Project Overview • Develop a robust control system that is capable of balancing a ball at a plate’s origin. • Allow users to control the plate and ball’s position with various devices. • Integrate interactive games. • Capable of fully autonomous operation. • Operate from AC wall power.

  3. System Block Diagram

  4. Progress Since PDR • Constructed physical model to demonstrate plate and motor interaction. • Communicated and translated touchscreen data to motor rotation.

  5. Mechanical System & Motor Interface

  6. Mechanical Design • From PDR:

  7. Mechanical Design

  8. Motor The motor: • Sparkfun • 4.8 to 6.0V • Analog actuation • Torque around 6kg*cm • Small Footprint • $12 • 180 degrees of movement

  9. Motor The motor: • Hitech • 4.8 to 6.0V • Small Footprint • Digital actuation • Torque around 343 oz-in • $70 • 90 degrees of movement

  10. Pivot We could have used: Ball bearing Fiberglass rod Shaved down hinges Rotating pivot

  11. Pivot Or, this nail.

  12. Arms Fiberglass is finally appropriate Rigidity issues may force us into aluminum arms

  13. Joints Binding posts were chosen over shoulder bolts Cheaper and easier to find Works for both arm-to-arm and arm-to-plate connections

  14. Motor-to-Arm Bolted it down with the included screws Acrylic base needed to secure screws Motor arm was imperfect

  15. Arm-to-Plate • We could have used: • Ball bearings • Pneumatics • Gears • Magnets

  16. Arm-to-Plate Or, a small hinge:

  17. Mechanical Design: Pending There are still questions to answer How will the second motor affect rotational stability? The motion is software limited, but should we physically limit this as well?

  18. Power Design

  19. Power Design • We are strongly considering the use of a computer PSU to supply the power to our project

  20. Power Design • Why? • Integrated/compact design • Efficiency • Safety • Very high quality control • No fried controllers!

  21. Power Design • PSU supplies 12V, 5V, and 3.3V lines • We will need to create a converter circuit on PCB to supply 6V to motors • PCB will be used for power distribution

  22. Control System

  23. Control System • The current control system is fairly theoretical • Testing will determine whether or not a different approach to controlling the ball will be necessary

  24. Control System • Control based off of second-order physical system • Forces on the ball were linearized with respect to angle to simplify system • Using a line of best fit of to gave a good approximation with . • Max difference between real and estimated accelerations is

  25. Control System

  26. Control System • Factoring in rotational inertia, the position of the ball can be modeled as • Sanity check: A constant angle input does cause a constant acceleration

  27. Control System • For the first design, a simple case was chosen. • A function that can control this was found to be

  28. Control System: Simulink Model

  29. Control System

  30. Control System • Possible issues: • This model is highly theoretical. It remains to be seen if all forms of disturbances can be rejected • If problems arise, a more robust approach will be needed • Microcontrollers don’t work in the Laplace domain!

  31. Plate Touchscreen Sensor

  32. Touchscreen Accuracy • Large touchscreen wasn’t accurate enough

  33. Touchscreen Accuracy • Smaller touchscreen showed smoother results

  34. Analysis • We need a more accurate large touchscreen that will still react to the ball’s weight when the touchscreen is at an angle

  35. Software System

  36. Software System • Simple main file • Initialize peripherals • Main loop • Check state and act accordingly • Header file for each peripheral • More modular • Keeps code readable

  37. Software Interrupts • Primarily soft interrupts • Best for an embedded environment • Easy to set flags which will determine states • Some hard interrupts • Good for emergency shutoff and other time-critical tasks

  38. Microcontroller Software Interface

  39. Hardware-Software Interaction & Microcontroller Usage • Hardware interaction with software, requires careful planning

  40. General hardware Interaction Computer Wifi/Eth. UART Debugging Hardware Cell Phone Bluetooth UART UART USB ADC DI/O User Input & ball feedback Joystick LCD screen & 7-segment debug display PIC32 Micro PMP Local Interface DI/O UART MotorControl PWM Touch Screen DI/O ADC Hardware HW Action

  41. On-chip hardware • Important PIC32 built in peripherals • 5 UART channels • 1x Parallel Buss • 16 Channel ADC • 5x 16 bit Digital Timers • 8x DMA channels

  42. Ethernet/Wifi • Wireless chip: 1x UART and 2x DMA channels to prevent the processor from having to wait for data. Computer PIC32 Micro Wifi/Eth. User Input & ball feedback UART Cell Phone

  43. Debugging Port • 1x UART and 2x DMA channels to keep the processor from having to wait for data to arrive. PIC32 Micro Debugging Hardware UART

  44. Bluetooth • 1x UART and 2x DMA channels to prevent the processor from having to wait to acquire data. PIC32 Micro Cell Phone Bluetooth UART User Input & ball feedback

  45. Joystick • Flexibility in choice • On-board USB 2.0 On-The-Go host support with dedicated DMA channels • Extra DI/O and ADC pins for a game port Joystick.

  46. Other Forms of User Input • Digital push buttons. Should be triggered by interrupts to provide highest response rate to user & button functionality User Input & ball feedback PIC32 Micro Local Interface DI/O UART

  47. LCD Screen PIC32 Micro LCD screen & 7-segment debug display • Fastest operation uses PMP bus to control parallel port enabled devices. PMP

  48. Table Control • 2x PWM outputs, one for each motor, each require a 32bit timer to output slow enough. • Requires 4 of the 5 16bit timers. • Needs to be updated at 50Hz to maximize control systems abilities. PIC32 Micro Table Control PWM

  49. Touch Screen User Input & ball feedback • 2x ADC pins • Need to be triggered to sample at a steady frequency in order to calculate velocity. Will likely involve the use of the 5th timer. • 2x DI/O pins • Needs to update at highest rate TBD. Hopefully 100-200Hz PIC32 Micro Touch Screen DI/O ADC

  50. Peripheral Utilization • Knowing this information, need to carefully program our processor otherwise system will fail to meet hard deadlines.

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